linux-kernel - Re: mmotm 2010-04-28

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Date:	Mon, 03 May 2010 16:48:52 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Valdis.Kletnieks@...edu
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: mmotm 2010-04-28 - RCU whinges

Le lundi 03 mai 2010 à 10:30 -0400, Valdis.Kletnieks@...edu a écrit :

> 
> I *really* thought we swatted a bunch of these - did the fixes not make it
> into linux-next or -mm?  Your patch fixed that one, but then:
> 
> [    9.128899] Netfilter messages via NETLINK v0.30.
> [    9.128919] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
> [    9.129108] CONFIG_NF_CT_ACCT is deprecated and will be removed soon. Please use
> [    9.129110] nf_conntrack.acct=1 kernel parameter, acct=1 nf_conntrack module option or
> [    9.129113] sysctl net.netfilter.nf_conntrack_acct=1 to enable it.
> [    9.129135] ctnetlink v0.93: registering with nfnetlink.
> [    9.129452] ip_tables: (C) 2000-2006 Netfilter Core Team
> [    9.129506] 
> [    9.129507] ===================================================
> [    9.129683] [ INFO: suspicious rcu_dereference_check() usage. ]
> [    9.129777] ---------------------------------------------------
> [    9.129872] net/netfilter/nf_log.c:55 invoked rcu_dereference_check() without protection!
> [    9.129969] 
> [    9.129969] other info that might help us debug this:
> [    9.129970] 
> [    9.130232] 
> [    9.130232] rcu_scheduler_active = 1, debug_locks = 0
> [    9.130407] 1 lock held by swapper/1:
> [    9.130525]  #0:  (nf_log_mutex){+.+...}, at: [<ffffffff81481154>] nf_log_register+0x57/0x10f
> [    9.130955] 
> [    9.130956] stack backtrace:
> [    9.131162] Pid: 1, comm: swapper Tainted: G        W   2.6.34-rc5-mmotm0428 #2
> [    9.131259] Call Trace:
> [    9.131370]  [<ffffffff81064832>] lockdep_rcu_dereference+0xaa/0xb2
> [    9.131466]  [<ffffffff814811db>] nf_log_register+0xde/0x10f
> [    9.131579]  [<ffffffff81b5ca28>] ? log_tg_init+0x0/0x29
> [    9.131689]  [<ffffffff81b5ca4d>] log_tg_init+0x25/0x29
> [    9.131800]  [<ffffffff810001ef>] do_one_initcall+0x59/0x14e
> [    9.131912]  [<ffffffff81b2e68a>] kernel_init+0x144/0x1ce
> [    9.132033]  [<ffffffff81003414>] kernel_thread_helper+0x4/0x10
> [    9.132146]  [<ffffffff81598a40>] ? restore_args+0x0/0x30
> [    9.132257]  [<ffffffff81b2e546>] ? kernel_init+0x0/0x1ce
> [    9.132370]  [<ffffffff81003410>] ? kernel_thread_helper+0x0/0x10
> [    9.132513] TCP bic registered
> 

You probably know this PROVE_RCU thing is new and reserved to
developpers ?

We yet have to change all spots were a rcu_dereference() was used
without rcu_read_lock(). Not a bug by itself, just lockdep is to be
instructed not to shout.

Maybe 30 patches already in, and maybe 30 other are still needed.



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